STATISTICAL CONNECTIONS BETWEEN THE PROPERTIES OF TYPE IA SUPERNOVAE AND THE B-V COLORS OF THEIR PARENT GALAXIES, AND THE VALUE OF H-0

Statistical connections between the properties of Type Ia supernovae ( SNe Ia) and the B-V colors of their parent galaxies are established. C ompared to SNe Ia in blue galaxies [(B-V)(T)(0) less than or similar t o 0.75], SNe Ia in redder galaxies have (1) a wider dispersion in the blueshifts of their Si II lambda 6355 absorption features, 10 days aft er maximum light; (2) more rapidly declining light curves; and (3) low er luminosities. Even when the spectroscopically peculiar, very sublum inous SNe Ia such as SN 1991bg are disregarded, SNe Ia in red galaxies are less luminous than those in blue galaxies by about 0.3 mag. When SNe Ia that are thought to have been significantly extinguished by dus t in their parent galaxies are disregarded, those in blue galaxies hav e observational absolute-magnitude dispersions of only sigma(obs)(M(B) ) = 0.20 and sigma(obs)(M(V))= 0.17, which implies that their intrinsi c absolute-magnitude dispersions are very small. We use six SNe Ia who se absolute magnitudes have been calibrated by means of Cepheids, whic h also indicate that the intrinsic absolute-magnitude dispersions of S Ne Ia in blue galaxies are very small, to calibrate SNe Ia in blue gal axies and obtain H-0 = 57 +/- 4 km s(-1) Mpc(-1). This value is in exc ellent agreement with that obtained by Saha and coworkers, in spite of the fact that they do not take into account any dependence of SN Ia a bsolute magnitude on the nature of the parent galaxy. Some implication s of the statistical connections between SNe Ia and the colors of thei r parent galaxies, for identifying the progenitor binary systems of SN e Ia and for using high-redshift SNe Ia to measure q(0), are briefly d iscussed.